Carbon felt, rockwool, ceramic wool: which padding for kojin-style stoves?

[Paiolo Montanel]

I love DIY alcohol stoves, and in this period I appreciate the simplicity and practicality of open-flame kojin-style and starlite-style alcohol stoves.

I’m building some of them, but I’d like to know how the various wicking materials compare: is there some material that offers better performance or some specific advantage over the other ones?

At the moment what I know (or what I experienced) is:

• carbon felt can have durability issue: when the flame is nearly over the carbon felt oxidizes and degrades
• rockwool tends to shrink over time, some stoves I built some time ago have the padding that lowered under the container rim negatively affecting performances (but this can probably be solved simply changing the insertion method: instead of using a “cilinder” of RW I have to try a rolled string of RW like we usually do with carbon felt, inserting it slightly pressed)
• ceramic wool is less “puffy” than rock wool (if you press it, it tend to keep the pressed shape) and probably doesn’t have the shrinking problem of rockwool.
• rockwool seems (in my experiments) a little better on vaporizing alcohol: the same container with the same quantity of padding if filled with rockwool gives me slightly faster stoves than with carbon felt or ceramic wool.
• Rockwool is lighter, for example a 30ml stove can be filled with 5 grams of ceramic wool / carbon felt, or with only 3 grams of rockwool

Do the stove builders of this forum have any more (or different) experiences with these (or others!) padding materials?

[James Marco]

I have used regular fiberglass insulation in the past. Yeah, you don’t touch it after it has been burned, but it lasts at least a week. ‘Corse, I only made two of the stoves. I prefer the open flame stoves, usually a chimney stove. But, I have gotten heat conservation down to the point of about 8-9gm per 850ml water (or about a quarter ounce per three 10oz cups, or, 4-5gm per/16oz, all from 34F/1C-icewater) with an inverted canister stove (Caffin’s V1/FMS-300t.)

Basically, that is 16-17 days out with a single 220gm canister. I am satisfied with that. The slight weight savings with alky cannot make up for the convenience of a canister stove.

(On longer trips I often take my SVEA, ultra reliable, even after stepping on it.)

[Paiolo Montanel]

Are there any comments on the topic from our stove professionists? ( @Jon Fong, @Dan Y…I’m talking about you! :-D )

[Jon Fong / Flat Cat Gear]

I defer to Dan.

I have done a lot of work with various stoves and ended up not being a fan of wicking materials.  From my prespective, I prefer open vessels as I like to option of being able to use denatured alcohol or gel alcohols & hand sanitizers.  Wicking materials have an advantage for new alcohol stove users (somewhat spill resistant) but if you know what you are doing its not a big deal.  My 2 cents.

[David Gardner]

I haven’t had any compression issues with ceramic wool over hundreds of burns in an open Kojin-style burner, and it never burns away. For me a couple of grams is worth the safety factor.

[Paiolo Montanel]

I absolutely agree with David… safety always come first (even if I agree that having no wick material leaves more building alternatives)

David, are you using the original Kojin stove or is it a DIY?

In the second case, can you give me the link where you bought the ceramic wool you use?

And a photo of the opened stove (just to see some details..)?

[David Gardner]

@piaolo: I have a Kojin but I was referring to a DIY stove made with aluminum screw-top spice/cosmetic containers. I bought both the containers and the ceramic wool from Amazon (although I did try to find the ceramic wool locally first):

If you’re thinking of making a similar one PM me and I can send you a container and some ceramic wool since they only come in bulk quantities.

[Renais A]

There is a very long thread on Whiteblaze discussing the fancee feast stove and its development.  I believe that somewhere in that thread it was noted that carbon felt, available from Amazon, was a good material for the wick.  The carbon felt didn’t have the fiber irritation  issues that fiberglass has, and was a good absorber, I believe. I think Dan (Zelph) on this site was the one who identified the final suitable material, maybe partly because he’d had issues making the stove with fiberglass.  I’ll leave it up to him to supply details, since it has been a while since I’ve looked at these stoves.

Renais

[DAN-Y/FANCEE FEEST]

Do the stove builders of this forum have any more (or different) experiences with these (or others!) padding materials?

 

Nothing different than what you already found out. You’re at a point where you can make an intelligent decision based on your findings. Have fun designing and testing under different conditions.

 

-carbon felt can have durability issue: when the flame is nearly over the carbon felt oxidizes and degrades
-rockwool tends to shrink over time, some stoves I built some time ago have the padding that lowered under the container rim negatively affecting performances (but this can probably be solved simply changing the insertion method: instead of using a “cilinder” of RW I have to try a rolled string of RW like we usually do with carbon felt, inserting it slightly pressed)
-ceramic wool is less “puffy” than rock wool (if you press it, it tend to keep the pressed shape) and probably doesn’t have the shrinking problem of rockwool.
-rockwool seems (in my experiments) a little better on vaporizing alcohol: the same container with the same quantity of padding if filled with rockwool gives me slightly faster stoves than with carbon felt or ceramic wool.
-Rockwool is lighter, for example a 30ml stove can be filled with 5 grams of ceramic wool / carbon felt, or with only 3 grams of rockwool

[Paiolo Montanel]

Really thanks David for the offer, but I’m from Italy so it wouldn’t be very practical to send me something! :-)

And anyway, I already have about 20 aluminium containers of various sizes (30ml/50ml mainly), good quantity of rockwool, some aliexpress carbon felt and a small sheet of ceramic fiber insulation…

I’m already experimenting with all of them without noting big differences… just want to know if there where something I were missing (for example, I learned only two days ago from this forum that carbon felt isn’t eternal like I thought!)

The carbon felt didn’t have the fiber irritation  issues that fiberglass has

Renais, unfortunately the carbon felt I bought on aliexpress is irritating… more or less like rockwool :-|

Nothing different than what you already found out. You’re at a point where you can make an intelligent decision based on your findings. Have fun designing and testing under different conditions.

Dan, the intelligent decision I can make at the moment from my findings is that… there is no real reason to use something different from cheap and easily available rockwool. It is ugly but works well: fast absorption, good fuel retention, good vaporization, lighter than other materials

I had some expectations for example from ceramic fiber insulation as it is used in kojin stove, and in an interview they said that “We got lucky in finding that filler materiel. I will keep this part a trade secret as long as I can.” but it doesn’t seems any better than rockwool (only less “puffy” and so easier to use to fill a container)

[Mole J]

The Kojin filling has a more “solid” suface than other ceramic wool burners I have  (Speedster and Myog)

Paiolo. Ceramic wool offcuts are available quite cheaply in UK on ebay. I’ll find a link for you.

 

[Mole J]

Paiolo.

No offcuts available right now.

In my search I also noticed a “Ridgidiser” silica spray that stiffens the surface of ceramic fibre/wool.  Maybe this is used to create the stiffer Kojin burner surface?

[Paiolo Montanel]

The Kojin filling has a more “solid” suface than other ceramic wool burners I have  (Speedster and Myog)

This “more solid surface” do you think give some advantage to kojin? (other than perhaps more durability)

To all the people that have both DIY ceramic fiber stoves and Kojin stoves: does the Kojin have any other particolar advantage (in addition to the sealed lid) over the DIY?

[Paiolo Montanel]

Mole, a cheap (but slow) source of ceramic fiber insulation is also Aliexpress:  https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20200604020528&SearchText=ceramic+fiber+insulation

About 10€ for a 30 x 60 x 1 cm cutoff… enough for 30-50 stoves!

[Mole J]

As far as I can see (after a few trips use maybe 50days) , in terms of boiling water the Kojin works in the same manner as  other mineral wadding wick stoves such as the Starlyte or DIY, or Speedster etc.

Having no metal mesh on the Kojin makes it easier to light than a meshed burner.  (my DIY burners no longer have mesh).

The “crispy’ top of the Kojin wick material helps prevent it compressing as I’ve noticed the insulation in my Speedster or diy burners can do. (no big deal really).

The green paint on the Kojin means the threads are more durably free moving than plain aluminium screw tops. The new gold (and other colour) tins might be similar, time will tell.

 

[Paiolo Montanel]

the Kojin works in the same manner as  other mineral wadding wick stoves

Do you mean that it has more or less the same performances with similar sized screw-top stoves?

Having no metal mesh on the Kojin makes it easier to light than a meshed burner.  (my DIY burners no longer have mesh).

I also prefer stoves without meshes!

The green paint on the Kojin means the threads are more durably free moving than plain aluminium screw tops. The new gold (and other colour) tins might be similar, time will tell.

We probably have already discussed this last problem somewhere: screw-top stoves often suffer lid-locking problems: alcohol in the long term corrodes aluminium and after some months of use often these stoves become difficult (or impossible!) to unscrew.

Some day ago I ordered these black tins in the hope that painted aluminium is less susceptible to this problem…lets see if they work:

 

[Mole J]

Do you mean that it has more or less the same performances with similar sized screw-top stoves?

Yes.  I happily used Starlytes for years, before trying Speedster stoves as being in the UK, they are easier to buy.  No difference really.

I got a Kojin a couple of years ago as it came with a Sidewinder by default.  I like it better than the others because no mesh means easier lighting in some circumstances.  But I’ve since made a few burners for myself and others using similar tins and ceramic wool.

If the diameter is the same, they all perform similarly.  Why wouldn’t they?

[David Gardner]

I rub a bit of graphite powder on the threads of my aluminum screw top containers to prevent sticking, although the biggest factor I have found to prevent sticking is to let the burner cool off completely and not over-tighten the lid afterwards. If the burner is capped while still warm it continues to push out some vapor, but when it cools off that creates a bit of negative pressure/vacuum that sucks the lid down so tight it won’t unscrew.

[DAN-Y/FANCEE FEEST]

Batting in both stoves are the same:

[Paiolo Montanel]

Sorry…I don’t know the first stove, what is it?

[DAN-Y/FANCEE FEEST]

Sorry…I don’t know the first stove, what is it?

 

It’s called the Pop-N-Lock stove. Sorry for the late answer.

Pop-N-LockStove

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